class_docstr: TorchRankerAgent implementation of the biencoder.
  
  It is a standalone Agent. It might be called by the Both Encoder.
docstr: Override from TorchRankerAgent.
docstr_tok: ["Override","from","TorchRankerAgent","."]
code: def vectorize_fixed_candidates(self, cands_batch):
      """
      Override from TorchRankerAgent.
      """
      return [
          self._vectorize_text(
              cand,
              add_start=True,
              add_end=True,
              truncate=self.label_truncate,
          )
          for cand in cands_batch
      ]
  
imports: from typing import Optional
  from parlai.core.params import ParlaiParser
  from parlai.core.opt import Opt
  from parlai.core.torch_ranker_agent import TorchRankerAgent
  from parlai.utils.torch import padded_3d
  from parlai.zoo.bert.build import download
  from parlai.utils.io import PathManager
  from .bert_dictionary import BertDictionaryAgent
  from .helpers import BertWrapper, BertModel, add_common_args, surround, MODEL_PATH
  import os
  import torch
  from tqdm import tqdm
label_desc: Use image node_id 6 for calling the BiEncoderRankerAgent obj's underlying member method code with example usage: obj.vectorize_fixed_candidates(cands_batch) and returns: unknown